Individual idler rollers of idler roller stations in belt systems for large mass flows can no longer be changed manually in case of needed repairs because of their high net weight. Furthermore, for reasons of occupational safety, a replacement of idler rollers is only allowed in the resting state of the belt system. Since belt systems equipped with girland idler roller stations are frequently used in practical operation, replacement devices known from the literature on the state of the art are mainly directed at the replacement of entire idler roller girlands with usually three or five individual idler rollers connected to one another. Such devices are known, for example, from the publications DD 148 504 A1, DE 2 163 726 A and DE 2 342 000 C2. They all have in common the fact that a conveyable auxiliary device next to the belt system is used for replacing the idler roller girlands in the sequence of lifting the conveyor belt, detaching and removing the idler roller girland having the worn-out individual idler roller or a plurality of worn-out idler rollers as well as inserting the new idler roller girland. The work performed during a changing process can be made easier and the time for the changing process can be shortened by means of these devices.
In idler roller stations with individual idler rollers fastened in idler roller carriers, only the defective idler roller needs to be replaced in case of a repair. An aid for the replacement intended for this is known, for example, from the publication DE 1 219 856 B. According to this invention, provisions are made for lifting the web belt by means of a carrier placed onto the frame of the belt system. This carrier is equipped with rollers and is displaced transversely to the longitudinal direction of the web belt, whereby the rollers of the carrier are adapted to the respective profile (slope) of the web belt. After the web belt was lifted to a sufficient extent, the affected idler roller of the idler roller station can be replaced, and the web belt is then lowered again. The lifting device is then removed again. This solution is especially suitable for smaller belt conveyors, whose individual idler rollers can be manually replaced without additional technical aids. The additional use of further technical aids is necessary in belt conveyors for large mass flows.
A device for lifting the web belt in the upper run and lower run of a conveyor to obtain sufficient mounting clearance when replacing the idler rollers present there is known from the publication DE 85 25 773 U1 by the designation “web belt cover lifter.” This device is a u-shaped subframe, which is hung in a height-adjustable manner on the support frame of the conveyor by means of claws from below on both sides. A lifting bar for lifting the web belt, which can be actuated in the vertical direction by means of a hydraulic cylinder, is located on the horizontal carrier of the subframe. After replacing the idler roller in question, the web belt is lowered again, and the subframe can be removed again.
A subframe for use in web belt conveyor systems, by means of which the conveyor belt is able to be selectively lifted in the upper run or in the lower run to replace idler rollers there if necessary or, in addition, to apply further idlers, is known from the company brochure “SAFE-GUARD™, BELT LIFTER” of the manufacturer ASGCO. This frame is placed onto the frame construction of the web belt conveyor system and can be adjusted in its height by increments. In an upper and a lower two-part horizontal carrier, it is assembled from both sides and thus can be connected to together by increments at intervals. A carrying belt which is fastened to one side of the subframe at the top and can be pulled by means of a tightening device on the other side of the subframe is used for picking up and for lifting the conveyor belt. This subframe has a lightweight-construction design and can consequently be favorably assembled and again removed at the site of use. Because of the assembly steps necessary for this from both sides of the web belt conveyor system, it is not suitable, however, for rapid replacement of a plurality of idler rollers at different sites of kilometer-long belt conveyor systems.